The present invention relates to a method and apparatus for making photographic color prints on color sensitive printing material, and more particularly to improvements in a method and apparatus for making color prints from color transparencies made on multiple-purpose film which was exposed by light of one of a plurality of different color temperatures, especially by daylight or artificial light. Still more particularly, the invention relates to improvements in a method and apparatus for making color prints by carrying out color corrections to deviate from gray in dependency on determination whether the exposure was made by daylight or artificial light. The determination involves ascertaining the ratio (difference or the quotient) of transmittances in two colors which are influenced by the color temperature of light by which the original was exposed, and comparing the resulting signal with a threshold value.
U.S. Pat. No. 3,029,691 to Goddard et al. discloses an apparatus for making color prints wherein integrated red transmittance is compared with integrated blue transmittance. It has been found that such comparison is not a reliable way of distinguishing between exposures by daylight or artificial light. This is due to the fact that the color shifts between such types of exposures are not most pronounced in red and blue colors and also because, in the case of average ratio of these colors, the difference is less when the intensity of light by which the original was exposed is low. Thus, resort to a fixed threshold value does not invariably guarantee optimum results.